Cinnamon is a Linux desktop which provides advanced innovative features and a traditional user experience.
The desktop layout is similar to GNOME 2; however, the underlying technology was forked from GNOME Shell.
The emphasis is put on making users feel at home and providing them with an easy to use and comfortable desktop experience.

Note: Cinnamon is not in the official repositories, so it is not supported by official Arch developers.

Note: See xinitrc for details, such as preserving the logind (and/or consolekit) session.

Configuration

Cinnamon is quite easy to configure - a lot of the configuration that most people will want can be done graphically. Its usability can be customized with applets and extensions, and also it supports theming.

Installing Applets/Extensions

The difference between an applet and an extension is that an applet is basically an addition to a panel, whereas an extension can completely change the Cinnamon experience and can do much more than an applet.

There are quite a few packages in the AUR (AUR package search for cinnamon). The process described here is a generic installation process.

Installing applets in Cinnamon is relatively easy. First visit Cinnamon Applets to see all of the current applets.
Download the zip file for the desired applet, and extract to ~/.local/share/cinnamon/applets/ or /usr/share/cinnamon/applets.
Then run

cinnamon-settings applets

to bring up the graphical applets manager. If the applet does not show up, press Template:Keypress and type r and press enter. This will restart gnome-shell and hopefully allow you to see your new applet.

The process is analogous for extensions, with the only difference being that directories titled "applets" can be changed to "extensions".

Creating Custom Applets/Themes

The official tutorial from Clement Lefebvre on creating an applet can be found here.

The official tutorial from Clement Lefebvre on creating a custom theme can be found here.

Troubleshooting

QGtkStyle was unable to detect the current GTK+ theme

If it turns out that QT applications are not able to detect the GTK theme, then you have to specify the theme explicitly. In case of the default Adwaita theme it would look like this: